1. Field of the Invention
This invention relates to a device for the hydraulic control of a clutch, especially for motor vehicles, comprising at least one emitter or receiver cylinder having a piston.
More particularly, the invention relates to a hydraulic control device for a motor vehicle clutch including at least one control cylinder, of the type in which the cylinder comprises a substantially tubular cylinder body in which there slides axially a piston which, through a front transverse face, bounds a hydraulic chamber, and which is in cooperation through a rear transverse face with a piston rod, wherein an aperture for connection of a pipe or a duct is open into the hydraulic chamber, and wherein the cylinder body is made of mouldable material such as plastics material.
Such a device is described for example in the document DE-U-2951 6488.
2. Description of the Related Art
In the latter, the piston is part of an assembly which includes a metallic piston skirt.
More precisely, the piston skirt has at its front end a projecting element on which the piston is formed by applied moulding. The skirt serves as a receptacle for two half shells which are so configured as to receive the head of the rod of the piston.
In addition, the piston carries a piston seal which is adapted to cooperate with a metallic guide sleeve mounted in the internal bore of the cylinder body and bounding the hydraulic chamber, while the cylinder body carries a secondary seal which is adapted to cooperate with the piston skirt. The cylinder body is for this purpose stepped internally in diameter, so that it has, at its rear end, an enlarged cross section whereby it can contain the secondary seal within it. A securing skirt is mounted in this larger section so as to retain the secondary seal.
Such a solution, which calls for a large number of components, is relatively costly and necessitates the presence of a dynamic piston seal carried by the piston and cooperating with the guide sleeve fixed to the cylinder body.
An object of the present invention is to overcome these drawbacks in a simple and inexpensive way.